Reaching 400ppm, a sobering milestone

Wednesday, May 1, 2013

In the next few days, a significant milestone will be reached: global greenhouse gas concentrations will surpass 400 parts per million (ppm) in the atmosphere. Already, at stations in the Arctic, the canary in the proverbial coalmine of climate change, readings above 400 are being recorded. What does this mean? Registering at 280ppm prior to the Industrial Revolution, this considerable change in atmospheric composition is set to thwart two decades of scientific calls to curb ‘dangerous anthropogenic climate change’. IPCC scientists have agreed that a 2C warming over the next century represents a ‘dangerous threshold’. It has been stated that this threshold cannot be surpassed if, globally, we think it is important for ecosystems to adapt naturally to climate change, for food production not to be threatened and for economic development to proceed in a sustainable manner. As temperatures increase so do non-linear responses that increase variability in the climate system. To prevent dangerous climate change, global atmospheric concentrations are to be curbed to 450ppm by 2100. Yet today’s recorded atmospheric concentrations are illustrating that we are on a precedent-setting emissions trajectory, likely to reach 450ppm – dangerous climate change - in the next couple of decades and concentrations of 550ppm or higher by 2100. Put in perspective, atmospheric concentrations have not been this high since probably the Pliocene epoch between 3.3 And 5 million years ago. This suggests that unless radical changes are made in the next few years, humans will be crafting a radically different future for our children and grandchildren.

Scientists have argued that there is a lag effect in the climate system. This suggests that atmospheric changes occurring now are likely to be felt, through warming, and other impacts decades into the future. In other words, our actions now are currently leaving a very different future for our grandchildren. Oceanographer and carbon cycle researcher, Tim Leuker from Scripps CO2 Group states this clearly: